Reversing and circulating valves are often used in a tubular string in a subterranean well for purposes of communicating fluid between the annular region that surrounds the string and a central passageway of the string. The valves may be operated via fluid pressure that is applied to the annular region, especially for the case in which gas exists in the central passageway of the string. Some of these valves are single shot devices that are run downhole closed and then opened in a one time operation. Valves that may be repeatedly opened and closed are typically complex devices that may have reliability problems and interfere with other valves in the string.
Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above.
In an embodiment of the invention, a technique that is usable with a subterranean well includes running a valve downhole in a first state and changing the valve to a second state in response to pressure that is applied to an annular region that surrounds the valve. The valve is changed between the first and second states by regulating a differential pressure between the annular region and an inner passageway of the valve.
In another embodiment of the invention, an apparatus usable in a subterranean well includes a valve, a first mechanism and a second mechanism. The valve controls communication between an annular region that surrounds the valve and an inner passageway of the valve. The first mechanism cause the valve to transition from a first state to a second state in response to pressure in the annular region. The second mechanism causes the valve to transition between the first state and the second state in response to a pressure differential between the annular region and the inner passageway.
Advantages and other features of the invention will become apparent from the following description, drawing and claims.